1. Technical Field of the Invention
The present invention generally relates to media streaming over a network. More particularly, and not by way of any limitation, the present invention is directed to a system and method for retrieving digital multimedia content from a network node in a client-server architecture.
2. Description of Related Art
With today's widespread use of the Internet as a major communication medium, computer networks are increasingly being used to transmit multimedia data (e.g., audio, full-motion video, pictures, et cetera). In the network-based context, one simple model of producing the information involves a client device requesting the downloading of the multimedia data from a server. Once downloaded, the client may then consume, or present, the information. This model is relatively easy to implement; however, it is non-optimal in that the client is required to wait for the downloading to complete before the presentation can begin. This delay can be considerable where large blocks of multimedia data are involved.
A more sophisticated model of producing information involves a content server at one network site “streaming” the multimedia information over the network to a client at another site. Streaming is a process in which packets, sent over an Internet Protocol (IP)-based network, are used to present material continuously to a recipient client as it arrives in substantially real time as perceived by the user. As such the client does not have to download and store a large file before displaying the material. That is, the client begins to present the information as it arrives (i.e., just-in-time rendering), rather than waiting for the entire data set to arrive before beginning presentation. Accordingly, at the client device, received data is buffered into a cache memory and continuously processed as soon as, or soon after, being received by the client for real time presentation of multimedia content.
Most streaming sessions include either live or video-on-demand (VOD) sources, and are typically associated with a single content source (i.e., a single VOD file or a single live source, e.g., a video camera). However, by adding the ability to combine sources into a single streaming session, much richer applications can be built based on multimedia streaming.
A “playlist” in its simplest form is just a list of media which could be used to simply manage playback of local content (i.e., audio files) or to control the streaming media sessions. When used in the context of multimedia streaming, playlists provide an extensible, dynamic method for delivering customizable audio and video content to users via streaming. A playlist represents a list of the media items that a server can stream to a client, which can include a mixture of program content and advertisements (ads), for example. Also, a playlist can be used to play several short clips or to provide a user with long blocks of programming.
In a client-server streaming architecture, two types of playlists may be provided: client-side playlists and server-side playlists. The main difference between the two types of playlists is that when the client-side playlists are used, a client player application has control of the streaming experience, whereas when server-side playlists are used, a streaming server has control of the streaming experience. Server-side playlists provide the ability for the streaming server to combine streams from multiple sources (in sequence) and stream to a client in a single session. The client need not (and may not even) be aware that there are multiple media sources. This is useful for providing ad insertion capability, or for applications where uninterrupted streaming (from multiple sources) is desired—i.e., where the client doesn't have to explicitly request streaming from each new source.
One of the issues when utilizing server-side playlists is to support dynamic playlist navigation, which is advantageous in providing the end-user with a compelling and useful user experience. Additionally, the playlist navigation functionality must be accomplished with minimal impact on the client device application due to significant client device resource constraints. Existing server-side playlist schemes, however, are deficient in that they do not support client-side navigational control of playlist seeking.